Electrochemical oxidation of 2,4,5-trichlorophenoxyacetic acid by metal-oxide-coated Ti electrodes

• Metal-oxide-coated Ti anodes are applied to eliminate 2,4,5-T from water.
• A high degradation efficiency of 2,4,5-T is obtained on Ti/SnO2–Sb/Ce–PbO2 anode.
• TOC removal ratio obtains >65% on PbO2 electrode after 30 min of electrolysis.
• An energy efficiency and 2,4,5-T degradation by-products are determined.

Electrochemical oxidation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) over metal-oxide-coated Ti anodes, i.e., Ti/SnO2–Sb/Ce–PbO2, Ti/SnO2–Sb and Ti/RuO2, was examined. The degradation efficiency of over 90% was attained at 20 min at different initial concentrations (0.5–20 mg L−1) and initial pH values (3.1–11.2). The degradation efficiencies of 2,4,5-T on Ti/SnO2–Sb/Ce–PbO2, Ti/SnO2–Sb and Ti/RuO2 anodes were higher than 99.9%, 97.2% and 91.5% at 30 min, respectively, and the respective total organic carbon removal ratios were 65.7%, 54.6% and 37.2%. The electrochemical degradation of 2,4,5-T in aqueous solution followed pseudo-first-order kinetics. The compounds, i.e., 2,5-dichlorohydroquinone and 2,5-dihydroxy-p-benzoquinone, have been identified as the main aromatic intermediates by liquid chromatography-mass spectrometry. The results showed that the energy efficiencies of 2,4,5-T (20 mg L−1) degradation with Ti/SnO2–Sb/Ce–PbO2 anode at the optimal current densities from 2 to 16 mA cm−2 ranged from 8.21 to 18.73 kW h m−3.

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